1. Field of the Invention
The present invention relates to an air conditioner for carrying out a heat pump refrigerating cycle with a non-azeotropic refrigerant mixture to exchange heat with air.
2. Description of the Prior Art
To protect the global environment such as the ozone layer and to prevent global warming, it is necessary to use alternative refrigerants instead of R22 for air conditioners. There are several alternatives whose cycle temperature and pressure are similar to those of R22. Most of the alternatives are non-azeotropic refrigerant mixtures that show a large temperature gradient during a vapor-liquid changing process, to deteriorate heat exchange efficiency.
Due to the large temperature gradient, the temperature of a refrigerant mixture in a two-phase state in a heat-pump refrigerating cycle is low at the inlet of an evaporator and high at the outlet thereof. The temperature of the same is high at the inlet of a condenser and low at the outlet thereof. This phenomenon reduces the mean effective temperature difference between the refrigerant mixture and air serving as a heat source, to thereby deteriorate the heat exchange efficiency of the refrigerant mixture compared with a single refrigerant. This results in deteriorating the performance of the heat-pump refrigerating cycle.
To improve the heat exchange efficiency between a non-azeotropic refrigerant mixture and air, a Lorentz cycle is effective. This cycle opposes the flow of the refrigerant mixture to the flow of air. Japanese Unexamined Patent Publication No. 1-39960 discloses an air conditioner that achieves the Lorentz cycle. This disclosure employs two kinds of four-way valves to oppose the flow of a refrigerant against the flow of air during cooling and heating cycles.
This disclosure is expensive and complicated because of the two kinds of four-way valves.